The present invention relates to keyboards and, more particularly, to a system, a keyboard and a method wherein key signals, representative of keystroke information, or key characters, are transmitted encoded in transmission formats based on a probability of use of one or more of the key characters.
Wireless keyboards transmit keystroke information, or key characters, to a computer via pulses of infrared light generated by a light emitting diode (LED). By turning the LED ON and OFF, a string of binary bits representative of the key characters are transmitted to the computer. In one format, a logical `0` bit is represented by an LED ON state and a logical `1` bit is represented by an LED OFF state. Using this format, transmitting a logical `0` bit requires more power than transmitting a logical `1` bit. As those skilled in the art will readily comprehend, the converse format may be used wherein a logical `1` bit is represented by the LED ON state and a logical `0` bit is represented by the LED OFF state. Using this converse format, transmission of a logical `1` bit requires more power than transmission of a logical `0` bit. For clarity and ease of description, only the former format will be described and discussed herein; however, the present invention may be advantageously implemented in conjunction with any transmission format.
Current wireless keyboards employ the same transmission formats, or schemes, used with hardwired keyboards. Typically, each of the keys of a keyboard are treated as a position in a matrix. The index of the matrix position of a particular key character is transmitted to the computer via pulses of light. Although reusing these "hardwire" schemes minimizes the need to write new control software, these schemes are not designed to minimize power consumption during data transmission. For a wireless keyboard, battery capacity is a critical design parameter. By reducing the power consumed when transmitting key characters to the computer, the battery can be advantageously made smaller while maintaining, or even extending, battery life between recharging. Another advantage of reduced power consumption is longer battery life.
Accordingly, there is a need in the art for a system, a keyboard and a method wherein key signals representative of key characters are transmitted in transmission formats which minimize power consumption, which provide error detection and which differentiate between key characters transmitted by different keyboards.